As Harald said, it is not needed to delete the page to remove the component. Also, if you remove the component presentation from the page, again you would not be able to delete the page and will receive the error "Item is in use". This is because this item although you have removed from the Page but from the Current version only and the older versions of the pages are still using that component. To resolve the issue, you also need to delete the older versions of the page using that component.
To delete a component, following should be checked:
- Check where all the component is in use by using
Where Used functionality
- If it is used in one or more pages - remove it from there, save the page and further remove all older versions which were using this component
- If it is used as an internal links in one or more component - remove it from there, save the component and remove all older versions of component which were using this component
- Try deleting the component and it should now not give you error - "Item in use"
- If now you get error "Item is published", you need to identify where all the component is published - Unpublish from all target where it is published
I hope it helps